Stop Steam auto-updating and breaking my mods:

Pretty much what the title says. I tried asking Reddit but apparently they're against mods now, because both my topics were deleted. Anyway, is there a way to do this? I have no intention of shady stuff, bought the game legit, blah blah blah. There's a launcher bypass mod...should I use that in a separate directory isolated from Steam? I know how to create modded and vanilla directories, so that's no problem. I just don't want to have to wait a week until, say, ScriptHook or Open IV update...or if T2 goes back on their decision, then I have a fully offline recourse.